This invention relates to a method for tuning a phased array antenna, and more particularly to a method of adjusting for differences in the effective lengths of the transmission lines to the elements of a phased array.
Phased array antenna systems are well known, one application being electronic steering of a beam for a tracking radar system. In such a system, the transmission line for each radiator element of the antenna includes a phase shift device which is controlled by a beam-steering computer. To provide a flat phase front under normal radiating conditions and maximize antenna bandwidth, the line lengths to each radiator element must be equal (or within other specified design) to within a few electrical degrees. Since this accuracy cannot be maintained in manufacturing, this may be accomplished in a "tuning" procedure by adjusting the line lengths, or by measuring the error and storing the value for use by the steering computer. There are a number of problems associated with equalizing line lengths and phase shifts.
Representative phased array systems are shown in U.S. patents to Kaiser, Jr., U.S. Pat. No. 4,213,131, Williams et al. U.S. Pat. No. 4,276,551, King U.S. Pat. No. 4,277,787, Lopez U.S. Pat. No. 4,191,960, Malm U.S. Pat. No. 4,189,733, Frazita U.S. Pat. No. 4,188,633, Reudink et al. U.S. Pat. No. 4,166,274, Steudel U.S. Pat. No. 4,160,975, and Piesinger U.S. Pat. No. 4,079,379.